Serena Williams may have turned 32 in September, but she is showing no sign of slipping from her perch at the top of the women's game.

In fact, worryingly for Victoria Azarenka and company, she appears to be getting better with age and heads to Istanbul on the back of arguably the most successful campaign of her career.

However, the year began with a rare disappointment when she slipped to a shock defeat to up-and-coming American Sloane Stephens in the quarterfinals of the Australian Open.

Her response to this setback was as emphatic as it was impressive. Starting in Miami, Williams embarked on a 34-match winning streak - the longest of her career - to dominate a clay court season that would bring four titles, culminating in a second French Open triumph.

On the back of this run, Williams headed to Wimbledon as an overwhelming favorite. But, in the biggest upset in a fortnight of upsets, Williams was undone over three dramatic sets by a truly inspired performance from the big-serving Sabine Lisicki in the fourth round.

This upset only appeared a whet the American's appetite for more silverware as she embarked upon an unusually busy second half of the season. Back on the clay, she won in Bastad, before tuning up for the US Open with victory in Toronto and a runner-up finish to Azarenka in Cincinnati.

This busy schedule did not seem to harm her chances in New York as she cruised into the final without dropping a set.

Here she faced Azarenka, and, fittingly, in a meeting of the WTA's two standout performers, they served up the year's highest-quality match. Eventually, though, it was Serena who prevailed to add a second major to this most remarkable of seasons.

"I'm very excited to have qualified for the TEB BNP Paribas WTA Championships and have the opportunity to return to Istanbul in October to defend my title," Williams said. "The support we received from the fans at last year's Championships was overwhelming and it's going to be a very special feeling returning to Turkey and playing in that incredible atmosphere again."